# Electrons in Atoms and Periodic Trends

## 27 terms · electronsinatoms

### Visible Light

Electromagnetic radiation (electric and magnetic component, perpendicular to one another)

### Wavelength

Distance between identical points on successive waves.

### Frequency

Number of waves that pass through a particular point in 1 second. 1 hertz = 1 cycle.
*All electromagnetic radiation travels through vacuum at c = 2.998 x 10^8 m/s
(c = wavelengthxfrequency)

### Quanta

Discrete units of energy. Max Planck proposed that energy is radiated continuously in little packets called ________. Energy of radiation is proportionate to frequency E=hv
h = 6.626 x 10^34 J.s

### Einstein's Photon

Finds that only when light of the "proper" wavelength hits the surface of a particular metal, were elctron ejected. Packets of energy = light = photons.

### Light

(physics) electromagnetic radiation that can produce a visual sensation. Part of electromagnetic spectrum Each color has own frequency, wavelength, and energy.

### (Bohr's model) Quantized?

Energy levels are quantized- have discrete energies. Each level is referred by quantum numbers! However, HIS MODEL IS WRONG BECAUSE THEY DO NOT ORBIT THE NUCLEUS IN CIRCULAR. PATHS.

### Quantum Mechanics versus Newtonian Mechanics

Describes motion of very small particles traveling at very high speeds; energy is gained/ lost in packets called quanta (photons for light energy). Behavior of visible objects at ordinary velocities.

### De Broglie

French nuclear physicist who generalized the wave-particle duality by proposing that particles of matter exhibit wavelike properties.

### Quantum numbers

The four numbers that define each particular electron of an atom. The Principle Quantum Number (n) describes the electrons' energy and distance from the nucleus/energy level. The Angular Momentum Quantum Number (l) describes the shape of the orbital in which the electron resides. The Magnetic Quantum Number (m) describes the orientation of the orbital in space. The Spin Quantum number describes whether the spin of the electron is positive or negative.

### Orbitals

s = spherical
p = dumbbell shaped
d = clover shaped
f orbitals....
Orbitals in the same sublevel are degenerate because they have the same energy!

### Hund's Rule

Most stable arrangement of electrons in subshells is one with greatest number of spins. Greatest number of spins/distance = electron-electon repulsion.
*Exceptions: Cr [Ar]4s13d5, Cu

### Aufbau Principle

Electrons enter orbitals of lowest energy first.

### Pauli Exclusion Principle

States that a maximum of two electrons may occupy a single atomic orbital, but only if the electrons have opposite spins

### Periodic properties

Properties vary as elements progress through period. Same pattern every period. Boiling point and density are periodic properties.

### Atoms Size

Determined by EFFECTIVE NUCLEAR CHARGE. Increases as charge increases. protons-electrons.

### Ionization Energy

Energy required to remove an electron from valence shell of an individual atom in gaseous state.

### Electronegativity

(chemistry) the tendency of an atom or radical to attract electrons in the formation of an ionic bond. Increases across a period.

### Isoelectronic

2 or more atoms have the same electron configuration.

### The molecular formula of an antibacterial drug is C17H18FN3O3. How many fluorine atoms are in a 150-mg tablet of this drug?

12 x 17 + 1 x 18 + 1 x 19 + 3 x 14 + 3 x 16 = = 204 + 18 + 19 + 42 + 48 = 331 g/mol 150 mg x 1 g/1000 mg = 0.150 g
0.150 g x 1 mol/331 g = 4.53 x 10-4 mol 4.53 x 10-4 mol x 6.02 x 1023 molec. x 1 F atom = 2.73 x 1020 F atoms

### Dry air about 20.95% oxygen by volume. Assuming STP, how many oxygen molecules are in a 75.0 g sample of air? The density of air is 1.19 g/L.

75.0 g x 1 L/1.19 g = 63.0 L x 0.2095 = 13.2 L x 1 mol/22.4 L = 0.589 mol 0.589 mol x 6.02 x 1023 molec./mol = 3.55 x 1023 molecules

### Linear

180 degrees (two or more atoms in straight atoms)

120 degrees

109 degrees

104.5 degrees

109.45 degrees

### Resonance

Shorter bonds, electrons are closer to nucleus (this is due the multiple places that double bonds/triple bonds can take form)